The lid was unlocked, according to the autopsy report. But the police report would probably be a more accurate place to find out the lid's exact condition when the maintenance man found it.
This has been discussed ad nauseum earlier in this and other threads, but the idea behind the accidental death is not that she committed suicide. The idea is that due to her mental state, she made decisions that lead to an accidental death. That is the simplest way I can put it. Let's say she was having an episode of manic psychosis. That would mean she was having delusional ideas, a sense of invincibility, and a compulsion to do certain things that simply wouldn't make sense to you or I. Therefore, for reasons that--again--we cannot logically work out, she decided to get into the cistern. At that point, whether because she could not get back out or some other reason, she ended up drowning. That is the most logical theory behind a bipolar-related accidental death in this case.
To try to make logical sense out of her decisions in a scenario like the one I just described is folly. Whatever thought processes she was having in the elevator video are not necessarily the thought processes she was having on the roof. People in these states are highly illogical, unpredictable, can shift from one delusion to another, and it is simply impossible to carry a line of logic through her behavior IF she was indeed in a bipolar psychosis. This kind of mental state is well-established, is fairly common among people with acute bipolar disorder, especially when they are changing, adding, or subtracting medications from their regimen. Fortunately, it doesn't usually lead to death, just as drug-related delusions don't usually lead to death, but both definitely CAN lead to death. And to clarify, bipolar people do not walk around in this state all of the time. It is an episode, and it might happen a few times in a bipolar person's whole life. Or more often, it just depends. It may never happen in people who are not acutely bipolar. These are just the facts of the psychology behind it.
Personally, I am always on the fence :fence: But I maintain a leaning toward accidental death due to mental illness, as I have for months. Our knowledge of what happened is not consistent enough to tie it to any one theory perfectly, but I think the preponderance of evidence suggests a very tragic accidental death. And the bizarre nature of it just adds a level of mystery that might not be there had she died in a car or something more common, but due to the same mental state. But I can understand that there are questions that leave open the possibility of foul play. I just think those questions wouldn't be scrutinized by us all so much if the means of death weren't so weird.